Reconstitution of ThiC in thiamine pyrimidine biosynthesis expands the radical SAM superfamily.
4-Amino-5-hydroxymethyl-2-methylpyrimidine phosphate (HMP-P) synthase catalyzes a complex rearrangement of 5-aminoimidazole ribonucleotide (AIR) to form HMP-P, the pyrimidine moiety of thiamine phosphate. We determined the three-dimensional structures of HMP-P synthase and its complexes with the product HMP-P and a substrate analog imidazole ribotide. The structure of HMP-P synthase reveals a homodimer in which each protomer comprises three domains: an N-terminal domain with a novel fold, a central (betaalpha)(8) barrel and a disordered C-terminal domain that contains a conserved CX(2)CX(4)C motif, which is suggestive of a [4Fe-4S] cluster. Biochemical studies have confirmed that HMP-P synthase is iron sulfur cluster-dependent, that it is a new member of the radical SAM superfamily and that HMP-P and 5'-deoxyadenosine are products of the reaction. Mössbauer and EPR spectroscopy confirm the presence of one [4Fe-4S] cluster. Structural comparisons reveal that HMP-P synthase is homologous to a group of adenosylcobalamin radical enzymes. This similarity supports an evolutionary relationship between these two superfamilies.
Chatterjee
Abhishek
A
Department of Chemistry and Chemical Biology, 120 Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Li
Yue
Y
Zhang
Yang
Y
Grove
Tyler L
TL
Lee
Michael
M
Krebs
Carsten
C
Booker
Squire J
SJ
Begley
Tadhg P
TP
Ealick
Steven E
SE
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D016935:Caulobacter crescentus / Q000201:enzymology / Q000378:metabolism*; D003839:Deoxyadenosines; D019143:Evolution, Molecular; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D011743:Pyrimidines / Q000096:biosynthesis; D013831:Thiamine / Q000096:biosynthesis
D001426:Bacterial Proteins; D003839:Deoxyadenosines; D007506:Iron-Sulfur Proteins; D011743:Pyrimidines; C105797:ThiC protein, Bacteria; C033714:5'-deoxyadenosine; C030986:pyrimidine; D013831:Thiamine